Maternal Instincts

Researchers Examine The Role Mother Nature Plays In Mothering

November 02, 1997|By Marilyn Kennedy Melia. Special to the Tribune.

Remember Binta Jua, the Brookfield Zoo gorilla, who captured the public's attention when she saved a toddler who had tumbled into the ape pit? Binta Jua catapulted to media stardom because she was the heroine of the highly unusual story of beast saves boy. A secondary, yet equally compelling, item in the widely reported event was that Binta Jua had received training on how to be a good mother, and that her instinct to rescue could have been part of the maternal compassion taught to her by the zoo keepers.

Aren't animals supposed to act solely on instinct? Aren't humans the ones who behave according to learned reason? The story may have struck a chord precisely because it reveals a truth that researchers have been uncovering: Maternal behavior is based on a blurry blend of learned experience and gut impulse in both animals and humans.

Like the question of whether intelligence is due to environmental factors or heredity, scientists have undertaken a spate of studies to understand the impact of hormones and other biological factors on mothering behavior.

Many women who have given birth aren't a bit surprised that there may be a biological basis for their urge to cuddle or protect their children. They believe that some maternal feelings spring forth so readily that they must have a physical basis, akin to an urge to satiate hunger or thirst.

"I definitely believe in a maternal instinct," says Sally Kurfirst, a Western Springs mother of a 5-year-old son and a 6-month-old daughter. "I didn't have much experience with newborns when I had my son, but I just knew exactly how to hold him, it really was instinctual."

Alison Fleming, a psychologist at the University of Toronto who has devoted much of her career to discerning Mother Nature's role in nurturing, says that the fluctuations of hormones at and after birth can give women "an edge or a slight head start (in mothering), but experience plays a huge role." Experience, says Fleming, includes prior interaction with infants as well as how women themselves were mothered.

In one of the few studies involving humans, Fleming found that increased levels of the hormone cortisol in first-time mothers increased their attraction to their infant's odor, enhanced their ability to recognize their infants, and enhanced their overall arousal and pleasure with their infant. Cortisol might not in itself be the magic mommy hormone, says Fleming. "The cortisol level might be a marker for a host of other (biochemical) things."

Researchers have discovered even more dramatic illustrations of a biological-maternal connection in animal studies. For instance, removal of certain olfactory structures in virgin rats prompt the non-mother rat to adopt certain maternal behaviors when they would normally avoid pups. In another study, researchers found the brain cells of a rodent who is characteristically dutiful with her pups -- the prairie vole -- to be highly receptive to the hormone oxytocin. (For humans, oxytocin stimulates contractions of the womb during childbirth and the release of milk during breast-feeding). In contrast, a related breed, the montane vole, is cold to its pups, and its brain cells have few oxytocin receptors.

Like race horses bred for speed on the track, can animals be bred for optimum maternal behavior? The jury is out on that, says Jay Rosenblatt, a psychobiologist at Rutgers University. "There is a genetic component to maternal behavior in animals. That means that if you manipulate the genetics you can actually knock out maternal behaviors; but that doesn't mean that individual differences in mothering performance are genetic."

Women who take to mothering with ease are quick to acknowledge a biological connection. "I was swept away by a powerful, overwhelming feeling when I had my son and daughter," says Mary (who asked that her last name not be used), the mother of two pre-teens. "It was a feeling that you would do anything for them. But I don't think all women have the same passion or maternal instinct."

Indeed not. For some women, a devastating despair or anxiety descends upon them when they meet their infant. The stress of a divorce, unemployment, a history of abuse as a child, or other crisis can interfere with maternal feelings and behaviors.

And in a cruel twist of nature, hormones can totally disrupt maternal inclinations, because they can prompt a woman into depression or other disorders. "Some women are susceptible to the swing in hormones (associated with birth), and that puts them at risk for depression or anxiety disorders" explains Susan Feingold, a Highland Park clinical psychologist, and president of the national organization, Depression After Delivery.

Although she regularly sees women who have problems that are prompted by hormonal changes associated with birth, Feingold does think there is a physically based maternal instinct. "Research sometimes comes along and validates what we know through common sense," she comments. "Our bodies and minds are connected; there's both a biological and emotional component to mothering."

Actually, in support groups for women with postpartum emotional disorders, Feingold urges mothers to search for and trust their own maternal instincts, which may be buried under their other problems. "A lot of women think that all other mothers are falling in love with their baby and that caring for their baby is natural and easy," says Feingold. "They can put a lot of pressure on themselves that makes them feel more inadequate. They need to learn to trust their own instinct."